<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
<html>
<head>
<title>Metadata Sidecar Files</title>
<link rel=stylesheet type='text/css' href='style.css' title='Style'>
<style type="text/css">
<!--
blockquote { margin-top: 1em; margin-bottom: 1em }
pre { color: #800; margin-left: 4em }
pre.code { color: #000; padding: 0; margin: 0 }
.lt { color: #666 }
.ind { margin-left: 2.5em }
p.a { margin: 1em 2em 0 1em }
p.b { margin: 0 2em 1em 2.2em; color: #666 }
p.c { margin: 1em 2em 1em 2.2em; color: #666 }
-->
</style>
</head>
<body>
<div class='index'>
<a href="#xmp">XMP Sidecar Files</a>
<br><a href="#xml">ExifTool XML Files</a>
<br><a href="#exif">EXIF Files</a>
<br><a href="#mie">MIE Files</a>
</div>
<h1 class=up>Metadata Sidecar Files</h1>
<p>Metadata for images and other file types may be stored in a separate metadata
file. These are the only files that exiftool can create from scratch. A common
example of this is the XMP "sidecar" file (which is discussed in the next
section in some detail). Other supported metadata file types are EXIF, MIE,
ICC and VRD. As well, ExifTool supports XML-format output, which can also be
used to generate metadata sidecar files.</p>
<hr>
<a name="xmp"></a>
<h3>XMP Sidecar Files</h3>
<p>There are a number of different ways to generate an XMP sidecar file with
exiftool, and the method you choose depends on your circumstances and
preferences. Below are a number of example commands which write an output XMP
file from information in a source file of any type.</p>
<p class=a>1. Copy same-named tags from all information types to preferred locations in XMP:</p>
<p class=b>(<code><i>SRC</i>.<i>EXT</i></code> is the source file name and
extension, and <code><i>DST</i></code> is the destination file name)</p>
<pre>exiftool -tagsfromfile <i>SRC</i>.<i>EXT</i> <i>DST</i>.xmp</pre>
<p class=a>2. Rewrite source file to destination XMP file:</p>
<p class=b>(same effect as above, but the command will exit with an error if the output XMP file already exists)</p>
<pre>exiftool <i>SRC</i>.<i>EXT</i> -o <i>DST</i>.xmp</pre>
<p class=a>3. Copy XMP, preserving original locations:</p>
<p class=b>(ie. copies XMP tags only to the same namespaces in the destination file)</p>
<pre>exiftool -tagsfromfile <i>SRC</i>.<i>EXT</i> -all:all <i>DST</i>.xmp</pre>
<p class=c>Advanced: Notice that <code>-all:all</code> is used above instead of
<code>-xmp:all</code> even though only XMP tags will be copied (since the destination
is an XMP file). This is because <code>-all:all</code> preserves the family 1 group
(ie. XMP namespace) while <code>-xmp:all</code> would copy tags to the preferred XMP
namespace, which may be different for XMP tags that exist in multiple namespaces.
To get the best of both worlds, <code>"-xmp:all>all:all"</code> may be used to
avoid the inefficiencies of assigning tags which aren't copied, while still
preserving the family 1 group.</p>
<p class=a>4. Rewrite source to XMP file, preserving locations:</p>
<p class=b>(same effect as above, but the command will fail if the XMP file already exists)</p>
<pre>exiftool <i>SRC</i>.<i>EXT</i> -o <i>DST</i>.xmp -all:all</pre>
<p class=a>5. Generate XMP from EXIF and IPTC using standard tag name mappings:</p>
<p class=b> (the <code>.args</code> files are available in the full ExifTool distribution)</p>
<pre>exiftool -tagsfromfile <i>SRC</i>.<i>EXT</i> -@ exif2xmp.args -@ iptc2xmp.args <i>DST</i>.xmp</pre>
<p class=a>6. Copy XMP as a block to an XMP file:</p>
<p class=b>(writing as a block is the only way to transfer unknown or non-writable XMP tags)</p>
<pre>exiftool -tagsfromfile <i>SRC</i>.<i>EXT</i> -xmp <i>DST</i>.xmp</pre>
<p>7. Extract XMP as a block and write to output XMP file: <span class=lt>(same effect as above)</span></p>
<pre>exiftool -xmp -b <i>SRC</i>.<i>EXT</i> > <i>DST</i>.xmp</pre>
<p class=a>8. Extract XMP as a block to an output text file with .xmp extension:</p>
<p class=b>(same effect as above, but the destination file name will be the same
as the source file, and this command will fail if the XMP file exists while the
previous command will overwrite an existing file)</p>
<pre>exiftool -xmp -b -w xmp <i>SRC</i>.<i>EXT</i></pre>
<p>9. Restore all XMP tags from an XMP sidecar file to XMP in a JPG image:</p>
<pre>exiftool -tagsfromfile <i>SRC</i>.xmp -all:all <i>DST</i>.jpg</pre>
<p class=a>10. Restore XMP as a block from an XMP sidecar file to a JPG image:</p>
<p class=b>(same effect as above except that any non-writable XMP tags would be
copied by this command, and the 2 kB of padding recommended by the XMP
specification is not added when copying as a block)</p>
<pre>exiftool -tagsfromfile <i>SRC</i>.xmp -xmp <i>DST</i>.jpg</pre>
<h4>Batch Processing</h4>
<p>When batch-generating sidecar files from many images, the <code>-o</code>
form of the command is easier to use:</p>
<pre>exiftool -ext <i>EXT</i> -o %d%f.xmp -r <i>DIR</i></pre>
<p>where <code><i>DIR</i></code> is the name of the directory containing the
images. Multiple <code>-ext</code> options may be used to process different
file types in a single command.</p>
<p>However, this technique can not be used to add information to XMP
sidecar files that already exist. For this, the <code>-tagsFromFile</code>
form must be used:</p>
<pre>exiftool -ext xmp -tagsfromfile %d%f.<i>EXT</i> -r <i>DIR</i></pre>
<p>But note that this command searches for the XMP files instead of the image
files, so it will not generate new XMP sidecar files if some images don't
have them. For this, the advanced (ie. tricky and confusing to use)
<code>-srcfile</code> option comes in handy:</p>
<pre>exiftool -ext <i>EXT</i> -tagsfromfile @ -srcfile %d%f.xmp -r <i>DIR</i></pre>
<p>The <code>-srcfile</code> option also allows multiple files to be specified,
in which case the first existing file is processed. This feature allows a
sidecar file to be used only if it already exists. For example, this command
writes to a sidecar XMP file if it exists, or the original file otherwise:</p>
<pre>exiftool -ext <i>EXT</i> -artist="Phil" -srcfile %d%f.xmp -srcfile @ <i>DIR</i></pre>
<p>Any of these commands may be used to process sidecar files stored in a
directory other than that of the original images by specifying a directory name
instead of "<code>%d</code>" in the filename format string. For example,</p>
<pre>exiftool -ext <i>EXT</i> -o <i>DSTDIR</i>/%f.xmp -r <i>SRCDIR</i></pre>
<p>will output XMP files to <code><i>DSTDIR</i></code> with information
from images in <code><i>SRCDIR</i></code>.</p>
<h4>Via the API</h4>
<p>By specifying different tags in the
<a href="ExifTool.html#SetNewValuesFromFile">SetNewValuesFromFile</a>
call, the above examples numbered 1-6 are programmed like this:</p>
<blockquote><table class='box'><tr><td><pre class='code'>
$exifTool-><a href="ExifTool.html#SetNewValuesFromFile">SetNewValuesFromFile</a>('SRC.EXT', @tags_to_copy);
$exifTool-><a href="ExifTool.html#WriteInfo">WriteInfo</a>(undef, 'DST.xmp');
</pre></td></tr></table></blockquote>
<p>and examples 7 and 8 use this general technique:</p>
<blockquote><table class='box'><tr><td><pre class='code'>
my $info = <a href="ExifTool.html#ImageInfo">ImageInfo</a>('SRC.EXT', 'xmp');
die "No XMP" unless $$info{XMP};
open FILE, '>DST.xmp';
print FILE ${$$info{XMP}};
close FILE;
</pre></td></tr></table></blockquote>
<hr>
<a name="xml"></a>
<h3>ExifTool XML Files</h3>
<p>Closely related to the XMP sidecar file is the XML file written using the
exiftool <code>-X</code> option. This file is RDF/XML format like XMP, but uses
exiftool-specific namespaces to give an exact mapping for all exiftool tag
names. This type of file is better suited to general information
storage/recovery since it facilitates copying of more original metadata than an
XMP file, but it doesn't have the portability of an XMP file or the ability to
store native-format data like a MIE file, and ExifTool can not be used to edit
XML files as it can with other metadata files. Below are example commands
demonstrating the use of exiftool XML files.</p>
<p>Create an exiftool XML sidecar file:</p>
<pre>exiftool a.jpg -X > a.xml</pre>
<p>Restore original meta information from exiftool XML file:</p>
<pre>exiftool -tagsfromfile a.xml -all:all a.jpg</pre>
<h4>Via the API</h4>
<p>There is no way to automatically produce a sidecar exiftool XML file via the
API since this function is accomplished with an output formatting option of the
exiftool application. However, the the API may be used to read and copy tags
from an exiftool XML file just like any other file format. When reading
ExifTool XML files, all tags except those in the <code>ExifTool</code>,
<code>File</code> and <code>Composite</code> groups are extracted with their
original family 1 groups to facilitate copying of these tags back into their
original locations in an image.</p>
<hr>
<a name="exif"></a>
<h3>EXIF Files</h3>
<p>EXIF files store EXIF information in the same format as in the APP1 segment
of a JPEG image (<i>with the exception that there is no size limit for an
EXIF file, while EXIF data in a JPEG image is limited to a maximum of 65527
bytes</i>). The three commands below illustrate techniques for copying the
entire EXIF block from a source image (<code><i>SRCFILE</i></code>) to an
output EXIF file (<code>out.exif</code>):</p>
<pre>exiftool -exif -b <i>SRCFILE</i> > out.exif
exiftool -tagsfromfile <i>SRCFILE</i> -exif out.exif
exiftool -o out.exif -exif <i>SRCFILE</i></pre>
<p>It is the specification of the <a href="TagNames/Extra.html">Extra</a> EXIF
tag in each of the above commands (the "<code>-exif</code>" argument) that
causes the EXIF information to be extracted as a block. JPEG, PNG, JP2, MIE and
MIFF files all support storage of EXIF data blocks in this format, although
exiftool does not current write MIFF images.</p>
<p>Tags may also be copied individually to and from an EXIF file, but remember
that this will not copy "unsafe" tags unless they are specified explicitly. This
technique must be used when creating an EXIF sidecar file if the source file
does not contain EXIF:</p>
<pre>exiftool -o out.exif -all -unsafe <i>SRCFILE</i>
</pre>
<p>or for all files in a directory:</p>
<pre>exiftool -o %f.exif -all -unsafe <i>DIR</i>
</pre>
<hr>
<a name="mie"></a>
<h3>MIE Files</h3>
<p>The <a href="MIE1.1-20070121.pdf">MIE file format</a> allows storage of
native binary meta information, and is the best option for saving metadata from
a file in its original format. Here are two examples that copy all individual
tags plus the ICC Profile to a MIE sidecar file:</p>
<pre>exiftool -tagsfromfile a.jpg -all:all -icc_profile a.mie</pre>
<pre>exiftool -o a.mie -all:all -icc_profile a.jpg</pre>
<p>And the following command performs the inverse operation, restoring metadata
in a JPG image from a MIE file:</p>
<pre>exiftool -tagsfromfile a.mie -all:all -icc_profile a.jpg</pre>
<p>Information can also be copied in block form to a MIE file. This allows
preservation of the original data structure as well as unknown and non-writable
tags. The command below copies the full EXIF segment as a block from a JPEG
image,</p>
<pre>exiftool -tagsfromfile a.jpg -exif a.mie</pre>
<p>which is functionally different from copying all writable EXIF tags
individually with a command more like this</p>
<pre>exiftool -tagsfromfile a.jpg -exif:all a.mie</pre>
<p>Block-writable tags are listed in the
<a href="TagNames/Extra.html">Extra Tags documentation</a>.</p>
<p>MIE files also have the ability to store information in compressed format with
the <code>-z</code> option (provided Compress::Zlib is installed on your system),
which may be useful if disk space is at a premium.</p>
<hr>
<i>Created Nov 12, 2008</i><br>
<i>Last revised Oct 7, 2012</i>
<p class='lf'><a href="index.html"><-- Back to ExifTool home page</a></p>
</body>
</html>